Cláudio R. Neri

Hexagonal mesoporous silica modified with copper phthalocyanine as a photocatalyst for pesticide 2,4-dichlorophenoxiacetic acid degradation

A new mesoporous catalyst was prepared by the reaction between 3-aminopropyltrimethoxisylane and Cu(II)-hexadecafluorophthalocyanine, followed by co-condensation of tetraethylorthosilicate around a micelle formed by n-dodecylamine. The surfactant was removed from the pores by continuous extraction with ethanol, giving the Si-CuF16Pc catalyst. This catalyst was characterized by SEM, FTIR, TGA, 29Si NMR, N2 adsorption and X-ray diffraction. SEM images confirmed that the catalyst material is formed by nanoaggregates with a diameter of 100 nm. N2 adsorption isotherms showed that Si-CuF16Pc has a surface area of approximately 200 m2 g(-1) and a porous diameter of 7.7 nm, characterizing the mesoporosity of this product. This novel material shows an excellent photocatalytic activity, degrading almost 90% of 2,4-dichlorophenoxyacetic acid (2,4-D) up to 30 min, while only approximately 40% of photodegradation was obtained in its absence.

Functionalized silica synthesized by sol-gel process

Abstract This work considers some aspects of the chemistry involved in the preparation and description of silicon oxide functionalized by sol–gel process. In this work we studied the synthesis and measured the properties of silicon oxide functionalized with 3-chloropropyl, through a sol–gel process. Thermogravimetic analysis, infrared spectra, and elemental analyses were measured. The samples were prepared in the following proportions of tetraethylorthosilicate (TEOS): 3-chloropropyl trimethoxisilane molar ratio: 1:0, 1:1, 2:1, 3:1 and 4:1. The thermogravimetric data for the resulting materials established the `minimum formulae 2:0, 3:1, 4:1, 7:1 and 11:1, respectively. As expected, the relative amount of water is inversely proportional to the presence of propyl groups. Infrared data show Si–C and –CH2– vibration modes at 1250 to 1280 and 2920 to 2940 cm−1, respectively. Thermogravimetric data and infrared spectra showed that inorganic polymers contained organic polymers.

Synthesis of Phthalocyanines−ALA Conjugates: Water-Soluble Compounds with Low Aggregation

Syntheses of two water-soluble phthalocyanines (Pc) containing 5-aminolevulinic acid (ALA) linked to the core structure are described. These compounds were prepared by using original functionalizations, and they present remarkable structural and photophysical features, indicating that they could be applied to photodynamic therapy (PDT).

Synthesis of hybrid silicates containing porphyrins incorporated by a sol–gel process and their properties

Abstract Porphyrin was incorporated in a silicate network, via a covalent bond, by grafting a functional group with 3-aminopropyltriethoxysilane, using a sol–gel process. We have carried out the synthesis and measured the absorption spectra, nuclear magnetic resonance spectra, infrared (IR) spectra, luminescence spectra and lifetime of these hybrid silicates, porphyrinosilicas. These samples contained the following free-base porphyrins: meso-tetrakis- p -chlorobenzoylporphyrin, meso-tetrakis-2,6-dichloro-3-chlorosulfonylphenylporphyrin. The obtained porphyrinosilicas have similar absorption and luminescence spectra to the free base porphyrins in solution. IR spectra confirm the formation of monomeric species. Lifetime measurement for porphyrinosilica reveals that 32%xa0±xa02% of porphyrin is covalently bonded to the silica network.

A novel chlorin derivative of Meso-tris(pentafluorophenyl)-4-pyridylporphyrin: synthesis, photophysics and photochemical properties

Photodynamic therapy (PDT) is based on the accumulation of a photosensitizer, such as a porphyrin or a chlorin, in a malignant tissue after its administration. Chlorins exhibit photophysical properties similar to those of the porphyrin macrocycles, but with intensified and red-shifted Q bands, making chlorin-containing systems even better candidates for PDT. In this contribution, we report the synthesis of 5,10,15-tris(pentafluorophenyl)-20-(4-pyridyl)porphyrin, (2) and its transformation to the novel chlorin derivatives 4, (5,10,20-tris(pentafluorophenyl)-15-(4-pyridyl)-tetrahydro-1H- N-methyl-pyrrolo [3,4-b]porphyrin and 5, (5,10,15-tris(pentafluorophenyl)-20-(4-pyridyl)-tetrahydro-1H- N-methyl-pyrrolo[3,4-b]porphyrin) by 1,3-dipolar cycloaddition with an azomethine ylide. The new products have been characterized by UV-Vis, 1H NMR and FAB-MS. The photophysics, photochemical and photobleaching properties of chlorin 4 have been evaluated. Its quantum yield of photobleaching (fPb, mol Einstein-1) was 0.047±0.014. In order to demonstrate the production of 1O2 when 4 is used as a photosensitizer, uric acid tests have been carried out. The results indicate that chlorin 4 can be considered a promising photosensitizer in PDT.

Characterization of iron(III)porphyrin-hydroxo complexes in organic media through UV-Vis and EPR spectroscopies

The interaction of OH− with Fe(TPP)+, Fe(TDCPP)+, Fe(TMP)+ and Fe(TFPP)+ in 1,2-dichloroethane was studied by titrating FeP solutions with aliquots of a solution of tetrabutylammonium hydroxide in acetonitrile. The number of OH− ions (n) coordinated to the FeP and the stability constants (βn) for the FeP-OH− complexes were calculated from UV-Vis absorbance data and iron spin states were determined through EPR spectroscopy. Fe(TMP)+ forms a high-spin mono-hydroxo complex, while Fe(TPP)+ and Fe(TDCPP)+ form high-spin bis-hydroxo complexes. To our knowledge, this is the first time that the formation of bis-hydroxo complexes from Fe(TPP)+ has been reported, and this was possible because the studies were carried out in basic organic media. In this same medium, FeIII-FeII reduction upon OH− addition to Fe(TFPP)+ was observed, without concomitant formation of the μ-oxo dimeric species [Fe(TFPP)]2O.

Synthesis and Study of the Photophysical Properties of a New Eu3+ Complex with 3-Hydroxypicolinamide

This work reports on the synthesis and characterization of a new complex of Eu3+ with the 3-hydroxypicolinamide ligand (Hhpa). Here we present an approach for obtaining bis[2-carbamoyl(κO)pyridin-3-olato(κO’)] lanthanide complexes, which were characterized through elemental analysis, thermal analysis, infrared and photoluminescence spectroscopies (emission, excitation, luminescence lifetimes, quantum efficiencies, Judd-Ofelt parameters and quantum yields). Although hpa can act as a bidentate ligand in different conformations, the results attest for the occurrence of a unique coordination site of low symmetry for the Eu3+ ions, in which two anionic hpa ligands coordinate the cations through an O/O chelating system. The phosphorescence of the synthesized gadolinium complex provides the energy of the triplet state, which is determined to be at 20,830xa0cm-1 over the ground state. This makes the Hhpa ligand very adequate for sensitizing the Eu3+ luminescence, which leads to a very efficient antenna effect and opens a wide range of applications for the complex in light emitting organic-inorganic devices.

b -diketonates of Eu3+, red phosphors, supported on sol-gel functionalised silica

Silica gel was functionalised with chloropropyl groups through the sol-gel process and then a b-diketone was incorporated into the support. Afterwards, Eu3+ ion and its chelates of 1,10-phenantroline (phen) and 2,2-bipyridine (bpy), red phosphors, were supported on such silica. Luminescence studies of Eu3+ bound to this new material have shown that there is an increase in the intensity of the emission when the ion is isolated by ligands in the silica matrix. The energy transfer from the ligands phen and bpy to Eu3+ ion was observed in the excitation spectra, which present new bands ascribed to the ligands and/or complex. The Eu3+-functionalised silica was characterised by TGA and FTIR. TGA analysis showed that there is a large loss of mass around 300 °C, which is ascribed to the organic part of the material. The FTIR spectra presented the vibration modes for Si-C and -CH2-. The luminescent properties of the ions surrounding the Eu3+ ion were studied. The decay curve displayed a bi-exponential behaviour, indicating that there is more than one site of Eu3+ on the surface of the silica.

Use of polymeric resin in the formation of SiO2 hybrid gels

Abstract A new organic–inorganic hybrid material with interpenetrating polymer networks was synthesized with a phase of SiO 2 made by sol–gel chemistry and an organic phase made from a polymeric resin obtained by polyesterification between metal chelate complexes (formed by metallic ions and α-hydroxycarboxylic acids) and a polyfunctional alcohol. One modification in this method consists in preparing organic polymers doped with europium III/dipicolinic acid or terbium III/1,2-phenylenedioxidiacetic acid complexes. Europium and terbium luminescent properties were used as probe to obtain structural information about the hybrid gel. To the organic polymers we added tetraorthosilicates to obtain transparent and luminescent organic–inorganic hybrid materials through the sol–gel process. Luminescent and infrared spectra and thermogravimetric properties were measured.

Synthesis, spectroscopy and photosensitizing properties of hydroxynitrophenylporphyrins

The hydroxynitrophenylporphyrins, 5,10,15,20-tetrakis(2-hydroxy-5-nitrophenyl)porphyrin and 5-mono(carboxyphenyl)-10,15,20-tris(2-hydroxy-5-nitrophenyl)porphyrin described in this work were prepared through Adlers method. These compounds were characterized by 1H NMR and light absorption and emission spectroscopy in the visible region. In order to demonstrate the involvement of 1O2 production, the uric (UA) acid test was carried out, which considers the decrease in the absorbance of UA at 293 nm following laser light irradiation of a solution containing UA and a photosensitizer. The results obtained demonstrate that these hydroxynitrophenylporphyrins can be considered as promising photosensitizers in PDT.